As its own name shows, this invention refers to a plate that impedes fire propagation toward the exterior of the compartment that covers, being these compartments placed where the aircraft engines as well as auxiliary power units are located. The new plate constitutive platform is made of composite material and it includes new light and resistant materials in the ventilation wire grid zone, whose disposition with, avoids fire propagation from the interior compartment where the engine is placed toward the rest of the aircraft.
The use of other kinds of flame arrestors for different purposes is well known at the current technical stage. Amongst all obtained patents, the following should be highlighted: U.S. Pat. No. 5,709,187 Flame Arrestor patent, which consists of a enhanced flame arrestor for a marine engine that includes an air box and passing combustion air intake and uniplanar flame arresting element mounted to the air box and passing combustion air through in one first direction into the air intake and blocking flame propagation in the opposite direction out of the air intake. The main disadvantage of this patent is its specific application for air intake tubes.
WO 00/73701 patent (Swiding Flashback Arrestor ) incorporates two monoliths (one acting as a mixer and the other as a flame holder) that have a plurality of channels defined by walls and are separately by a gap. The downstream monolith includes at least one channel which has a spatial orientation whereby a swirl is imparted to a fluid traversing there through. The main disadvantage of this patent is its specific application for gas turbines.
Another common characteristic observed in the current technique relating flame arrestors is the disposition between fire retaining elements and the exterior part as a labyrinth, so that fire decreases and even extinguishes in its way out.
Usually those compartments that contain aircrafts engines are known as hot compartments and compulsory require certain kind of refrigeration. Engine and A.P.U. compartments are covered by a composite bulkhead not only for military aircrafts, which do not have to meet fire specifications, but also for civil aircrafts, which must meet F.A.A. specification, and which incorporate refrigeration systems inside the casing.
In order to reduce the total weight of the aircraft as much as possible a flame arrestor would be made from a composite bulkhead, obviating the refrigeration system that should be included inside the engine compartments. It has to be considered that these kinds of bulkheads do not comply with any specification relating to fire protection. This way, some elements are usually incorporated on to the same composite bulkhead being used. These elements together isolate the inside and impede fire propagation toward the exterior of the compartment.
This type of barrier meets not only fire protection requirements, but also the applicable structural requirements that require bearing the weight of one operator on the mentioned bulkhead. The flame arrestor subject to the invention is part of a bulkhead that extends over the whole periphery of casing where the engine or the A.P.U. is installed. A flame arrestor that meets F.A.A. (Federal Aviation Authority) requirements on fire protection is obtained from bulkheads currently in use by changing their constituent materials and introducing other new materials with a specific disposition.
Amongst the elements mentioned, there is a metallic wire grid, circular and with thickness through holes distributed over its inner surface, which sits peripherally on a metallic plate, that is directly located onto the composite bulkhead. On the inner side if the bulkhead, another metallic plate is installed with equivalent dimensions to the outer one; This way a coating for the bulkhead is obtained, reinforcing the zone directly affected by flames. The edges of the composite bulkhead inner circle are chamfered and reinforced with a metallic flanged cylinder.
Between the bulkhead chamfered edges and the metallic flanged cylinder composed of welded disc on a cylindrical ring, there is a cavity that in case of fire acts as an insulating element for the hole edge. At the same time the cavity conducts toward the interior of the casing, any gases that may be generated inside composite, due to the temperature rise caused by the combustion. Some holes are located in the flanged cylinder that reinforces the lower side of composite bulkhead coinciding with the void zones that exist between bulkhead edges and reinforcement metallic flanged cylinder. Hot gases accumulated in void zone flow into the engine compartment out of flame arrestor and fire propagation to other adjoining units.
Besides the previously mentioned elements, a thin metallic plate, preferably Titanium, is placed parallel to the bulkhead. It has an octagonal shape and its edges rounded off toward the engine compartment. The distance established for the plate location, as well as its fastening, is carried out by using threaded bolts which, combined with their corresponding nuts, are the flame arrestor fastening systems.
From all the previously described the following advantages of the flame arrestor now invented should be highlighted: fulfillment with F.A.A. (Federal Aviation Authorities) standards regarding the bulkhead fire resistance requirements, generalization in the use of the platform in any existing aircraft engine, application simplicity of this flame arrestor constitutive elements and, finally easy conversion of existing platforms that do not meet the applicable specifications in new fire resistant platforms.
In order to make the explanation easier a drawing sheet has been attached, in which a practical case of this invention scope is represented.